Universal light emitting diode illumination device and method

ABSTRACT

Disclosed is a method and apparatus for providing a light emitting diode and driving circuitry integrated into a component module that will retrofit common incandescent lightbulb applications. The disclosed embodiments will perform with high efficiency at a wide operating voltage range with a very small size allowing for the incorporation within the envelope and form of existing lightbulb bases. Therefore, a single universal LED light bulb module can be used to replace the dozens of conventional LED and incandescent lights currently being used. The electronic circuitries used to drive the LEDs are extremely compact and consequently can be incorporated in nearly any standard bulb base.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/716,633, filed on Mar. 3, 2010, which is a continuation of U.S.patent application Ser. No. 12/244,645, filed on Oct. 2, 2008, issued asU.S. Pat. No. 7,699,494, which is a continuation of U.S. patentapplication Ser. No. 11/831,791, filed on Jul. 31, 2007, issued as U.S.Pat. No. 7,448,770, which is a continuation of U.S. patent applicationSer. No. 11/026,796, filed on Dec. 31, 2004, issued as U.S. Pat. No.7,300,173, which is a continuation-in-part of U.S. patent applicationSer. No. 10/820,930, filed on Apr. 8, 2004, issued as U.S. Pat. No.7,318,661, which claims the benefit of and priority to U.S. ProvisionalPatent Application No. 60/502,495, filed on Sep. 12, 2003, the entiredisclosure of each of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a light emitting diode illuminationdevice and method and more specifically to a light emitting diode anddriving circuitry integrated into a component module that will retrofitcommon incandescent lightbulb applications.

BACKGROUND

Currently, lightbulbs for low power lighting applications such asflashlights are dominated by incandescent lights that use hot filamentsto provide radiant energy. The radiation that is emitted by hotfilaments is spread over a wide spectral range and much of the energy iswasted owing to emission outside the visible range. Moreover, suchfilaments must be designed for the specific voltage of operation, e.g.,a bulb designed for 2.7 volt (V) operation cannot be used for operationat a higher, 3.6 V level without causing immediate premature failure.Similarly, operating at a lower voltage, such as 2.2 V lowers the lightoutput to unacceptable levels. In addition, wide varieties of low powerlightbulb bases have been established over the last hundred years. Evenwithout considering additional application factors, the combination ofthese two factors alone means that hundreds of distinct lightbulbs mustbe manufactured in order to meet specific application demands.

Light emitting diodes (LEDs) have operating advantages with respect toincandescent lights. LEDs can emit light in a narrow range ofwavelengths so that a high proportion of the input energy is convertedinto light emitted within a specific wavelength envelope, resulting inapplication specificity and high efficiency. Such lights have very longlife compared to incandescent lights (50,000 hours vs. 3-30 hrs forincandescent flashlight bulbs). Like incandescent bulbs, LEDs require aspecific, narrow operating voltage range, ordinarily from 3.2 V to 4 V.Higher voltage results in premature failure and lower voltage results inlittle or no light output. Conventional LED illumination devices sharehigh application specificity, resulting in a similarly large number ofdistinct products as with ordinary incandescent bulbs. This discouragesconventional LED use, as retailers must now carry twice the alreadyexcessive inventory of the same product. In addition, LED lightbulbs forvarious voltages are commonly fabricated by incorporating a ballastresistor serving as a current limiter. This technique wastes energy anddoes not markedly increase the voltage operating range. LED circuitswith current and voltage regulation have been utilized in applicationssuch as traffic lights where large numbers of LEDs are packaged togetherto provide a bright, long lasting and highly efficient lighting.However, in a traffic light application, space is not a limitation, andso fairly complex and bulky electronic circuits have been used to meetthese specialized needs.

SUMMARY

The present invention overcomes the disadvantages and limitations of theprior art by providing a light emitting diode and driving circuitryintegrated into a component module that will retrofit commonincandescent lightbulb applications. The disclosed embodiments willperform with high efficiency at a wide operating voltage range with avery small size allowing for the incorporation within the envelope andform of existing lightbulb bases. Therefore, a single universal LEDlight bulb module can be used to replace the dozens of conventional LEDand incandescent lights currently being used. The electronic circuitriesused to drive the LEDs are extremely compact and consequently can beincorporated in nearly any standard bulb base. Because the operatingvoltage of these circuits is so wide, they are able to effectively drawout the last bit of energy present in a battery pack, providingexcellent efficiency and capacity. For example, a 6 V battery pack willstill operate the LED at full brightness when it only delivers slightlyin excess of 1.5 V; in other words, the batteries are effectively “dead”with respect to conventional light bulbs, but this embodiment stilloperate as though the batteries were fully charged. In fact, there islittle or no change in the light output from 6 V down to approximately1.5 V, allowing for the use of nearly all the energy available from thebattery. In addition, a 3 V battery pack and a 6 V battery pack forexample, would use the exact same light bulb as described in thisinvention, being completely interchangeable.

The universal LED light bulb module can be driven by a circuit that iseither a constant voltage output or a constant current output. Theconstant current design is preferred since light output is directlyproportional to current, and slight differences in the LED manufacturerequire different operating voltages for a given light output. Thisconstant current circuit is a high frequency, low power dc/dc converter.The high frequency of operation allows components of small size to beused. The essential feature of this circuit is a voltage comparator thatregulates the voltage to a specified value to achieve the desiredoutput. An inductor is charged to achieve the desired voltage output inthe circuit. In the constant current implementation, a current sensingresistor is used to provide the voltage feedback. Although oftendesigned for DC-to-DC operation in the range discussed, the disclosedconstant current circuit can be easily modified to work at highervoltages by using for instance, a zener diode resistor combination, orto operate as an AC/DC converter by adding a rectifier circuit. Otherfeatures such as light sensors, pulse circuits etc., can be added toprovide additional features such as flashing operation or dimming.Various logic signals can be easily adapted to introduce addedfunctionality to the embodiments. For example, a single activation of apower switch could provide a low output light, a second activationproducing a medium output light, a third activation producing a highoutput light, and a fourth activation shutting off the light. Multiplecolored LEDs can also be used to vary the desired colored output.

An embodiment of the present invention may therefore comprise auniversal LED lamp that is capable of replacing incandescent bulbs andthat operates at various voltages comprising: a standard bulb base thatis adapted to fit into standard bulb sockets; a printed circuit boardthat is electrically connected to a voltage input contact of thestandard bulb base that is capable of fitting in the envelope of thestandard bulb base; a driving circuit mounted on the printed circuitboard that includes a solid state voltage comparator that regulates theinput voltage to maintain an output voltage at a predetermined constantvalue within a predetermined range of input voltages that are both aboveand below the predetermined output voltage; an LED that is electricallyconnected to the output of the driving circuit and physically connectedto the printed circuit board.

An additional embodiment of the present invention may also comprise amethod of producing a universal LED lamp that is capable of replacingincandescent bulbs that operate at various voltages comprising:providing a standard bulb base that is adapted to fit into standard bulbsockets; electrically connecting a printed circuit board to a voltageinput contact of the standard bulb base; mounting a driving circuit onthe printed circuit board that includes a solid state voltagecomparator; regulating the input voltage with the driving circuit tomaintain an output voltage at a predetermined constant value within apredetermined range of input voltages that are both above and below thepredetermined output voltage; fitting the printed circuit board withinthe standard bulb base; electrically connecting an LED to the output ofthe driving circuit; and, physically connecting the LED to the printedcircuit board.

The disclosed embodiments offer the advantage of providing a universalLED light bulb module with long life and high efficiency at a wideoperating voltage range with a very small size allowing for theincorporation within the envelope and form of existing lightbulb bases.The LED illumination module has the further advantage over conventionalincandescent type bulbs by providing a precise wavelength outputenvelope, resulting in high efficiency and application specificity.Additionally, the high frequency of operation in the drive circuitryallows components of small size to be used and allows the device toeffectively draw out the last bit of energy present in a battery pack.Additional ancillary features that are not currently available inincandescent bulbs such as light sensors, pulse circuits etc., can beadded to the drive circuitry to provide additional features toconventional products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the invention, including areflector.

FIG. 2 is a perspective view, without showing a reflector.

FIG. 3 is a schematic diagram of an exemplary circuit implementing thedriving circuit of this invention.

FIG. 4 is similar to FIG. 1, except that it employs multiple LEDs and aconverging lens.

FIG. 5 is a flow diagram of a flashlight related method.

FIG. 6 is another flow diagram of a flashlight related method.

FIG. 7 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.

FIG. 8 is a drawing showing a typical embodiment of a universal LEDillumination device in relation to an incandescent lightbulb.

FIG. 9 is a schematic representation of a DC circuit used for a typicalembodiment of a universal LED illumination device.

FIG. 10 is a drawing showing a typical embodiment of a universal LEDillumination device in relation to an incandescent flashlight bulbapplication.

FIG. 11 is a drawing showing a typical embodiment of a universal LEDarray illumination device in relation to an incandescent flashlight bulbapplication.

FIG. 12 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.

FIG. 13 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.

FIG. 14 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit a halogen lightbulb application.

FIG. 15 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit a focused beam incandescent flashlightapplication.

FIG. 16 is a schematic representation of a DC circuit used for a typicalembodiment of a universal LED illumination device.

FIG. 17 is a schematic representation of an AC circuit used for atypical embodiment of a universal LED illumination device.

The numeric identifiers in the figures correspond to the elements asfollows:

2 a transparent lens adapted to emit a majority of the lightperipherally

3 at least one light-emitting semiconductor chip

4 a small (round) printed circuit board

6 hard protective material encasing the electronic components 15 and 17

9 a socket for the LED module comprising 2 and 3

12 the pin to be electrically connected to the positive side of thebattery pack

14 the pin to be electrically connected to the negative side of thebattery pack

15 an exemplary integrated circuit (IC) component

17 another integrated circuit (IC) component

21 replacement reflector (shorter than original), if necessary

22 lens replacing normal protective transparent window

23 exemplary focused light ray

302, . . . , 333 components of the driving circuit

DETAILED DESCRIPTION

A perspective view of a preferred physical form for this invention isshown in FIG. 2. A cross-section of FIG. 2 appears as FIG. 1.

In FIG. 1, the standard light bulb power connector is shown as pins 12and 14, respectively conductively connected to the positive and negativepower source of the flashlight (presumably batteries). The light emitter3 typically would be an LED chip embedded in a transparent plastic lens2 and a driving circuit embedded in a module. (Of course, potentiallymore than one light emitting chip could be used, perhaps to simulatewhite light with multiple chips each emitting a different wavelength.)

Also in FIG. 1, the transparent lens 2 of the light emitter preferablyis so shaped that it refracts a majority of the emitted light laterallytoward the reflector 21. Reflector 21 would ideally have the shape of aportion of a paraboloid, with the light-emitting chip 3 on thecenterline (axis of revolution) near the focal point of the paraboloid.Alternatively, reflector 21 could simply be a portion of a cone. Thereflector of the Mini Maglite® and its housing may be rotated withrespect to the flashlight barrel and is attached thereto by thehelically threaded, mating portions of the barrel and housing. As thereflector is rotated its focal point is moved along the centerlinerelative to the light-emitting chip 3. As the focal point is movedrelative to the chip 3, the shape of the beam reflected off thereflector 21 is changed from a broad cone-like beam to a narrower beam.Light ray 23 is exemplary of all such rays composing the beam.

Because of the tiny size of the incandescent bulbs used in miniatureflashlights, a inexpensive, conventionally-implemented driving circuitfor a solid state replacement source of light would not fit within thevolume envelope of the miniature bulb. Therefore, it must be at leastpartly exterior to that envelope. The driver circuit module of thepresent invention comprises a small conventional printed circuit board4, circuit components (such as commercially available integratedcircuits represented by elements 15 and 17 in FIG. 1), a potting layer 6protecting those circuit components, a socket 9 for the support andconductor leads of the light emitter (LED), and pins 12 and 14equivalent to the connector of the original incandescent bulb. (In thecase of other types of miniature bulbs, the pins 12 and 14 might beinstead some other type of connector, such as a standard screw orbayonet light bulb base.) The dimensions of the module for the MiniMaglite®, for example, would be about 15 mm in diameter and about 3 mmthick—larger than the original incandescent bulb.

Furthermore, if the flashlight has a lens housing which rotates, themodule 6 provides a low friction surface in order for the reflector 21to readily turn as it contacts module to preserve the focusingcapability or to preserve the on-off switch capability.

Still further, the protective material of the module 6 must facilitateradiation and conduction of heat away from the light emitters and fromthe supporting circuit elements in module 6. The material, for instance,may be a thermally conductive epoxy. To increase the transfer of heatfrom that material to the surrounding atmosphere, the module isgeometrically shaped to maximize surface area within the limited volumeto facilitate the radiation of heat from the emitters and the module.Besides the gross geometry of the module 6, the surface of the modulemay be textured to increase its surface area. To increase the radiationof unwanted heat, the reflector itself could be fashioned from athermally conductive material such as stamped aluminum. This would beparticularly effective, because it directly contacts the module 6 in thepreferred embodiment and because it has a relatively large surface area.

In flashlights like the Mini Maglite®, there would not be any availablespace for the driver circuit module. So, for such cases, a replacementreflector is an optional, additional element of the invention. Thereplacement reflector 21 would be essentially identical to the originalreflector, except that a small rear portion is removed to account forthe thickness of the driver circuit printed circuit board 4 andprotective potting 6. Assuming that the light emitting chip 3 occupiesapproximately the same optical location as the filament of the originalincandescent bulb, the shape of the replacement would be equivalent tothe original, except for the small portion removed from the smaller openend. (Otherwise, the replacement reflector 21 would be modified slightlyin shape to account for the new position of the chip relative to theoriginal position of the filament. That is, the relationship of thefocal point of the new reflector to the chip would be about the same asthe relationship of the focal point of the old reflector to thefilament.)

An alternative embodiment is shown in FIG. 4. In it there are severalsmaller LEDs instead of one larger one. The disadvantage of thisarrangement is that the LEDs are off the midline axis, so the light willbe spread out farther than with the case of FIG. 1. One partial remedywould be to replace the usual flat protective window of the flashlightwith a (converging) lens. One advantage of multiple LEDs is that theycould generate an approximation to white light by mixing the colors ofseveral LEDs (such as that of red, green, and blue LEDs). Using adiffusing lens 22 (or reflector 21) which has a stippled or pebbledsurface would smooth the appearance of the light, especially whenmultiple LEDs are present.

A preferred embodiment of the driver circuit for this invention is shownin schematic diagram in FIG. 3, which shows a DC circuit used for atypical embodiment. A high frequency, low power DC-to-DC convertercircuit is utilized to drive the LED 302. The high frequency ofoperation allows components of small size to be used. A positive voltagesource is introduced at +Vin 312 and branched to a capacitor C1 316 andinductor L1 320 and to two inputs (Vin 324 and EN 326) of a switchingcircuit 304. The solid-state switching circuit 304 regulates the inputvoltage Vin 324 to a specified value to achieve a switched output at SW328 by receiving an enable signal EN 326 branched from Vin 324. Theinductor L1 320 is charged during the ON cycle phase of SW 328 anddischarges in the OFF cycle phase to achieve the desired switchedvoltage output driving a Schottky diode D1 306 that in turn drives theanode side 308 of the output LED 302 and capacitor C3 318 which isterminated to ground. This Schottky diode D1 306 allows the current toflow in only one direction to the anode side 308 of the LED 302 via SW328. The Schottky diode D1 306 also assures that there is a quantity ofrectification of the AC signal flowing through the circuit so that theLED only sees half of the AC cycle, effectively acting as a DC signal.Capacitor C3 318 becomes a charge reservoir, averaging out what wouldotherwise be a sinusoidally varying voltage with one half of the sinewave missing.

The cathode side 310 of the LED 302 is passed through ground via R-4 322and branched to the feedback FB pin 332 of the switching circuit 304through resistor R3 320. The FB pin 332 acts as half of an operationalamplifier that is comparing the voltage at R-4 322 above ground, to areference voltage, (i.e., 1.23V). When the voltage at R4 322 reaches itsreference voltage, the switching circuit 304 stops supplying current.The FB pin 332 therefore serves as feedback reference within theswitching circuit 304, determining the current values by comparing afeedback voltage to its internal reference and deciding whether more orless charge is needed, thereby regulating the circuit current. −Vin 314,capacitors C1 316 and C3 318, resistor R4 322 and the ground terminal330 of the switching circuit 304 are all terminated to ground.

In a constant current implementation, a current sense resistor is usedto provide the voltage feedback. An integrated circuit of small size,Texas Instruments TPS61040 or TPS61041 is suitable for this purpose.Although designed for DC-to-DC operation in a suitable voltage range,the circuit can be easily modified to work at higher voltages by using azener diode resistor combination, or to operate as an AC-to-DC converterby adding a rectifier circuit. Additional operational features such aslight sensors, timers, etc., could be added to provide for dimming orautomatic shut-off functions. Multiple colored LEDs can be used to varythe desired colored output. Although only one LED is shown, several LEDscan be combined in a series circuit, parallel circuit or series-parallelcircuit up to the limitations of the IC used. An appropriate LED may bechosen for use in this circuit to suit the particular application andsized to closely match the bulb dimensions and intensities ofconventional lamps. The circuit shown in FIG. 3 can be implemented ineither a constant voltage output design or a constant current outputdesign. The constant current design has advantages since light output isdirectly proportional to current, whereas slight variations in the LEDmanufacture require different operating voltages for a specific lightoutput.

As shown in method 400 in FIG. 5, an incandescent light source in anincandescent flashlight can be replaced with at least one solid statelight source and a cooperating printed circuit board such that the atleast one solid state light source is located within an areacircumscribed by a light reflecting surface and the cooperating printedcircuit board is located within an overall envelope of the flashlight,(step 402). A light reflector arrangement of the incandescent flashlightcan be replaced with a smaller light reflector arrangement within alight reflector housing, and the steps of replacing the incandescentlight source and reflector arrangement are carried out without changingthe dimensions of the overall envelope of the flashlight, (step 404).

As shown in method 500 in FIG. 6, an incandescent light source can bereplaced in an incandescent flashlight with at least one solid statelight source and a cooperating printed circuit board such that the atleast one solid state light source is located within an areacircumscribed by a light reflecting surface and the cooperating printedcircuit board is located within an overall envelope of the flashlight,(step 502). A given battery compartment volume of the flashlight can bereduced such that the dimensions of an overall envelope of theflashlight remains unchanged, (step 504).

While this invention is described above with reference to a preferredembodiment, anyone skilled in the art can readily visualize otherembodiments of this invention. For example, circuits other than the onedescribed could be used. Also, other shapes for the refractive LEDenclosure 2 could be used. Therefore, the scope and content of thisinvention are not limited by the foregoing description. Rather, thescope and content are delineated by the following claims. While thisinvention is susceptible to embodiment in many different forms, thereare shown in the drawings and will be described herein in detailspecific embodiments thereof with the understanding that the presentdisclosure is to be considered as an example of the principles of theinvention and is not to be limited to the specific embodimentsdescribed.

FIG. 7 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.As illustrated in FIG. 7, an LED illumination device 700 may be made upof an LED lamp 702 that is connected to a printed circuit board 704 byan anode 726 wire at an LED anode connect 708 and a cathode 728 wire andan LED cathode connect 710 located on the printed circuit board 704.This printed circuit board 704 contains electronic circuitry placed incircuit area 706 and is of small size enabling the printed circuit board704 to fit within the envelope of a standard bulb base 716. Electricalconnections from the circuit board 704 to the bulb base 716 are made viaa V_(in) positive 712 connector in connection with +V_(in) contact 720on the external distal apex of the bulb base and a V_(in) negative 714connector in connection with −V_(in) contact 722 on the side edge of thebulb base 716. The +V_(in) contact 720 and the −V_(in) contact 722 areisolated from one another by an insulator 718. The aforementionedconfiguration allows the LED illumination device 700 to conform to astandard bulb envelope thereby allowing the embodiment to be utilized asa replacement for conventional incandescent bulbs in a variety ofapplications. This replacement of incandescent lights with LEDillumination affords numerous operating advantages. The disclosed LEDembodiments are able to emit light in a narrow wavelength rangeresulting in the bulk of the energy consumed by the device to be emittedas visible light, thereby delivering much higher electrical to opticalconversion efficiency than incandescent technology. Although red, green,and blue LEDs can be combined to produce white light, UV emitting LEDscan be used with fluorescing materials to produce white light forgeneral illuminating applications. Such LEDs have very long lifecompared to incandescent lights (50,000 hours vs. 3-30 hrs forincandescent flashlight bulbs) in addition to the high efficiency ofLEDs.

FIG. 8 is a drawing showing a typical embodiment of a universal LEDillumination device in relation to an incandescent lightbulb. Asillustrated in FIG. 8, an LED illumination device 800 is contrasted withan incandescent lightbulb 850. A comparable size and functional relationis demonstrated in the disclosed embodiment of an LED lamp 802 driven bya logic circuit 806 in connection with a standard bulb base 816,mimicking the envelope of an incandescent bulb 826 with a resistivelighting filament 828 in a standard bulb base 816. Both designs includea base 816 with +V_(in) contact, 820 and 830, and −V_(in) contacts 822and 832 isolated from one another by insulators 818 and 834. FIG. 8further demonstrates the ability of an LED illumination device 800 toretrofit conventional incandescent bulbs in a variety of applications.

FIG. 9 is a schematic representation of a DC circuit used for a typicalembodiment of a universal LED illumination device. A high frequency, lowpower DC-to-DC converter circuit is utilized to drive the LED 902 in thedisclosed embodiment illustrated in FIG. 9. The high frequency ofoperation allows components of small size to be used. A positive voltagesource is introduced at +V_(in) 912 and branched to a capacitor 916 andinductor 920 and to two inputs (V_(in) 924 and EN 926) of a switchingcircuit 904. The solid-state switching circuit 904 regulates the inputvoltage V_(in) 924 to a specified value to achieve a switched output atSW 928 by receiving an enable signal 926 branched from V_(in) 924. Theinductor 920 is charged during the ON cycle phase of SW 928 anddischarges in the OFF cycle phase to achieve the desired switchedvoltage output driving a Schottky diode 906 that in turn drives theanode side 908 of the output LED 902 and capacitor 918 which isterminated to ground. This Schottky diode 906 allows the current to flowin only one direction to the anode side 908 of the LED 902 via SW 928.The Schottky diode 906 also assures that there is a quantity ofrectification of the AC signal flowing through the circuit so that theLED only sees half of the AC cycle, effectively acting as a DC signal.Capacitor 918 becomes a charge reservoir, averaging out what wouldotherwise be a sinusoidally varying voltage with one half of the sinewave missing.

The cathode side 910 of the LED 902 is pass through ground via resistor922 and branched to the feedback FB pin 932 of the switching circuit 904through resistor 921. The FB pin 932 acts as half of an operationalamplifier that is comparing the voltage at resistor 922 above ground, toa reference voltage, (i.e., 1.23V). When the voltage at resistor 922reaches its reference voltage, the switching circuit 904 stops supplyingcurrent. The FB pin 932 therefore serves as feedback reference withinthe switching circuit 904, determining the current values by comparing afeedback voltage to its internal reference and deciding whether more orless charge is needed, thereby regulating the circuit current. −V_(in)914, capacitors 916 and 918, resistor 922 and the ground terminal 930 ofthe switching circuit 904 are all terminated to ground.

In a constant current implementation, a current sense resistor is usedto provide the voltage feedback. An integrated circuit of small size,Texas Instruments TPS61040 or TPS61041 is suitable for this purpose.Although designed for DC-to-DC operation in a suitable voltage range,the circuit can be easily modified to work at higher voltages by using azener diode resistor combination, or to operate as an AC-to-DC converterby adding a rectifier circuit. Additional operational features such aslight sensors, pulse circuits etc., can be added to provide for flashingoperation or dimming. Multiple colored LEDs can be used to vary thedesired colored output. Although only one LED is shown, several LEDs canbe combined in a series circuit, parallel circuit or series-parallelcircuit up to the limitations of the IC used. An appropriate LED may bechosen for use in this circuit to suit the particular application andsized to closely match the bulb dimensions and intensities ofconventional lamps. Hence, by combining this circuit on a small formfactor circuit board into an existing bulb base, together with the LED,a product can be obtained that has nearly identical or even superiorform, fit, and function to traditional incandescent lamps. The circuitshown in FIG. 9 can be implemented in either a constant voltage outputdesign or a constant current output design. The constant current designhas advantages since light output is directly proportional to current,whereas slight variations in the LED manufacture require differentoperating voltages for a specific light output.

Because the circuit shown in FIG. 9 can be extremely compact, it can beincorporated in nearly any standard bulb base. With this implementation,the operating input voltage of the circuit is very wide (at least 1.5 Vto 7 Volts), effectively drawing nearly all of the energy present in thebattery pack, thereby making excellent utilization of available power.The disclosed circuit will allow the LED light bulb to maintain constantlight output under a wide range of voltage input. For example, a 6 Vbattery pack will still operate the LED, at full brightness, when itonly delivers slightly in excess of 1.5 V. In other words, when thebatteries are effectively “dead” with respect to conventional lightbulbs, this embodiment will continue to operate as though the batterieswere at full capacity. There is little or no change in the light outputfrom 6 V down to approximately 1.5 V, allowing for the use of nearly allthe energy available from the battery. In addition, a 3 V battery packand a 6 V battery pack for example, would use exactly the same lightbulb, being completely interchangeable.

The circuit detailed in FIG. 9 can be readily expanded or combined withadditional circuitry to introduce a variety of additional functions tothe device. These functions may include but are not limited to: adimming feature that allows the bulb to be used at one or morebrightness levels; brightness levels being used as a power saving modeor as an indication of low battery or deficient external power; anautomatic shut-off timer function; light output color changes; variablelight beam direction; backup power supply; combination of incandescentand LED lighting; voice activation; or the like.

FIG. 10 is a drawing showing a typical embodiment of a universal LEDillumination device in relation to an incandescent flashlight bulbapplication. As illustrated in FIG. 10, a flashlight body 1022containing a standard incandescent bulb 1030 with a standard bulb base1028 is fixed within a reflector 1020 to reflect and project a beam oflight through reflector cover 1024. This same configuration can beutilized with an LED lamp 1002 as the light source. In this application,a flashlight body 1012 contains an LED lamp 1002 with a standard bulbbase 1028. A circuit board 1004 containing the necessary driver circuitand electronics for the LED lamp 1002 is housed within this standardbulb base 1028 thereby providing an overall envelope which is nearlyidentical to it in the incandescent bulb. The LED lamp 1002 is similarlyfixed within a reflector 1010 to reflect and project a beam of lightthrough reflector cover 1014. This embodiment enables a single circuitand lighting device to be used with a variety of bulb bases therebyaffording is an economic advantage both in manufacturing as well as tothe user who may transfer the product to more than one application orstock one kind of bulb for multiple applications. This circuit isdesigned to adapt to various AC or DC power sources and accommodate thedifferent voltages that may be present.

FIG. 11 is a drawing showing a typical embodiment of a universal LEDarray illumination device in relation to an incandescent flashlight bulbapplication. As illustrated in FIG. 11, a flashlight body 1122containing a standard incandescent bulb 1130 with a standard bulb base1128 is fixed within a reflector 1120 to reflect and project a beam oflight through reflector cover 1124. This same configuration can beutilized with an LED array 1102 of lamps as the light source. In, thisapplication, a flashlight body 1112 contains an LED array 1102 of lampswhile still utilizing a standard bulb base 1128. The LED array 1102 canbe mounted on a flat surface, such as a printed circuit (PC) board 1108.In this embodiment, a PC board is equipped on its top surface with oneor more LEDs connected in either a series or parallel circuit. This topsurface may (or may not) contain electronic components such as ICs,resistors, capacitors and the like. The bottom surface may also containcircuitry and its associated electronic components such as a DC-to-DCconverter circuit 1104 and may contain an electrical connector 1106which mates to a complimentary connector mounted within a standard bulbbase 1128. The bulb base 1128 in this example is used to make electricalconnections to an electrical source (not shown) and deliver the power tothe wafer-shaped PC board 1108. This DC-to-DC converter circuit 1104 isdesigned to adapt to various power sources and accommodate the differentvoltages that may be present. Similar circuits may be utilized to allowthe aforementioned embodiments to be powered by either AC or DC sourcecurrent. The LED array 1102 is similarly fixed within a reflector 1110to reflect and project a beam of light through reflector cover 1114.This embodiment enables a single circuit and lighting device to be usedwith a variety of bulb bases thereby affording is an economic advantageboth in manufacturing as well as to the user who may transfer theproduct to more than one application. This single circuit is designed toadapt to various AC or DC power sources and accommodate the differentvoltages that may be present.

FIG. 12 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.As illustrated in FIG. 12, an LED 1202 is mounted to a wafer PC board1204 such that the LED 1202 will project light outward and approximatelyperpendicular to the top surface of the PC board 1204. The LED 1202 ismounted to the PC board 1204 by an anode 1226 and cathode 1228attachments on the top surface. The converter and logic circuit 1206 canbe mounted on either or both sides of the wafer PC board 1204 and areshown in FIG. 12 on the bottom surface. This LED 1202 and associatedconverter and logic circuit 1206 are connected to a 3-pin connector 1212that facilitates an easy connection to a standard bulb base 1216. Thisconnection is made through a single anode 1226 connector located in thecenter of the 3-pin connector 1212, and two cathode 1228 connectors thathave been bifurcated from the LED 1202 and placed lateral to the anode1226. This cathode geometry allows the LED and circuitry module to beplaced into connection in either left or right orientation within the3-pin connector 1212.

FIG. 13 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit an incandescent lightbulb application.As illustrated in FIG. 13, a set of LEDs 1302 (each on an LED holder1330) is mounted in a triangular pattern to a wafer PC board 1304 ineither a series or parallel configuration such that the LEDs 1302 willproject light outward and approximately perpendicular to the top surfaceof the PC board 1304. The LEDs 1302 are mounted to the PC board 1304 byan anode 1326 and cathode 1328 attachments for each LED 1302 on the topsurface. The converter and logic circuit 1306 can be mounted on eitheror both sides of the wafer PC board 1304 and are shown in FIG. 13 on thebottom surface. These LEDs 1302 and associated converter and logiccircuit 1306 are connected to a 3-pin connector 1312 that facilitates aneasy connection to a standard bulb base 1316. This connection is madefrom each LED through to a single anode 1326 connector located in thecenter of the 3-pin connector 1312, and two cathode 1328 connectors thathave been bifurcated from each LED 1302 and placed lateral to the anode1326. This cathode geometry allows the LED and circuitry module to beplaced into connection in either left or right orientation within the3-pin connector 1312.

FIG. 14 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit a halogen lightbulb application. Asillustrated in FIG. 14, a group of LEDs 1402 is mounted to a PC board1404 such that the LEDs 1402 will project light outward andperpendicular to the top surface of the PC board 1404 to produce an LEDhalogen replacement bulb 1400. The converter and logic circuit 1408 canbe mounted on either or both sides of the wafer PC board 1404 and areshown in FIG. 14 on the top surface. This top surface can be coated witha reflective surface 1412 to increase light output intensity byreflecting light otherwise lost and enhance heat dissipation of the LEDsand circuitry. These LEDs 1402 and associated converter and logiccircuit 1408 are made to connect employing “bump ends” 1406 that adaptthe PC board to fit and electrically connect within halogen bulbfixtures. The large area of PC board 1404 space additionally allows foradditional circuitry 1410 to be readily added to either side of thedescribed embodiment.

FIG. 15 is a drawing showing a typical embodiment of a universal LEDillumination device to retrofit a focused beam incandescent flashlightapplication. In particular products such as flashlights, a reflectiveparabolic reflector is an integral part of the product's feature set. Incertain applications, the reflective reflector can be moved up and downby rotating a portion of the flashlight's barrel. When this is done, thereflector moves up and down thereby moving the bulb above, through andbelow the prime focus of the parabolic reflector. This has the effect offocusing or dispersing the light beam to give either a narrow spot orbroad beam. Because LEDs usually contain focusing optics, a forwardmounting as described above is usually an adequate implementation.However, to take advantage of unique features that may already bepresent in existing applications, an aftermarket implementation thataddresses these specific features and associated needs is necessary.

As illustrated in FIG. 15, a flashlight body 1522 containing a standardincandescent bulb 1530 with a standard bulb base 1528 is fixed within areflective parabolic reflector 1520 to reflect and project a beam oflight through reflector cover 1524. The reflector 1520 acts to reflectthe light emanating from the filament in a standard incandescent bulb1530 to a focused light beam 1540. A similar configuration can beutilized where an LED replacement bulb is designed to allow light toemanate from one or more LEDs 1502 mounted to a PC board 1508 inflashlight body 1512. In this embodiment, the planar axis of the PCboard 1508 is mounted within a standard bulb base 1528 and positionedparallel to a focused beam of light 1550. As illustrated in FIG. 15, twoLEDs 1502 are used, one each on either side of a metal core PC board1508. The LEDs 1502 in this embodiment send their light directly towardsthe surface of the parabolic reflector 1510 and project as a focusedlight beam 1550 through reflector cover 1514.

The LEDs 1502 are positioned such that they are in the same positionrelative to the focal point on the parabolic reflector 1510 as thefilament 1538 is in the incandescent bulb 1530 it replaces. In this way,the focusing/defocusing feature works as it was intended to since thelight is emitted either above or below the prime focus. Hence, both theuser and the manufacturer can employ this product and gain theadvantages of high efficiency and long life of the LEDs without losingthe optical features of the product. Either surface of the PC board 1508may also contain circuitry and associated electronic components such asa DC-to-DC converter circuit 1504 and may contain an electricalconnector that mates to a complimentary connector (not shown) mountedwithin a standard bulb base 1528. The bulb base 1528 in this example isused to make electrical connections to an electrical power source (notshown) and deliver the power to the PC board 1508.

Because the generation of excessive heat is a great detriment to the LEDand associated circuitry, additional elements can easily be added to thedisclosed embodiments such as the incorporation heat sink devices 1521or materials in or on the PC board. A metal core PC board 908A is shownin this embodiment to demonstrate the ease in which heat dissipationtechniques can be adapted to the aforementioned embodiments.

FIG. 16 is a schematic representation of a DC circuit used for a typicalembodiment of a universal LED illumination device. Although the circuitof FIG. 9 is well suited for constant current operation of low powerLEDs where the current required is on the order of 20 mA, the senseresistor 922 in that circuit dissipates power that may be less thanoptimal at higher current levels. An alternative higher current, highfrequency, DC-to-DC converter circuit that generates a constant poweroutput, ideal for higher current applications, is utilized to drive theLED 1602 in the disclosed embodiment illustrated in FIG. 16.

A positive voltage source is introduced at +V_(in) 1612 and branched toan inductor 1620 and to inputs V_(CC) 1624 of an IC driver circuit 1604(i.e., Zetex ZXSC310). The solid-state driver circuit 1604 regulates theinput voltage V_(CC) 1624 to a specified value to achieve a switchedoutput at V_(Drive) 1628, which in turn drives an external transistor1634. The inductor 1620 is charged during the ON cycle phase oftransistor 1634 and discharges in the OFF cycle phase to achieve thedesired switched voltage output driving a Schottky diode 1606 that inturn drives the anode side 1608 of the output LED 1602 and capacitor1618 which is terminated to ground. This Schottky diode 1606 allows thecurrent to flow in only one direction to the anode side 1608 of the LED1602 via transistor 1634. The Schottky diode 1606 also assures thatthere is a quantity of rectification of the AC signal flowing throughthe circuit so that the LED only sees half of the AC cycle, effectivelyacting as a DC signal. Capacitor 1618 becomes a charge reservoir,averaging out what would otherwise be a sinusoidally varying voltagewith one half of the sine wave missing. A low value sensing resistor1620 is connected to the ON phase of external transistor 1634 andminimizes power dissipation. The transistor switches ON and allowscurrent to flow through resistor 1620, where the voltage drop providesthe necessary current sense input to the current sense pin 1632 of theIC 1604.

The cathode side 1610 of the LED 1602 is pass through ground. When thecurrent at resistor 1620 reaches its reference current, the comparator1604 stops supplying current. The current sense pin 1632 thereforeserves as feedback reference within the driver circuit 1604, determiningthe current values by comparing a feedback current to its internalreference and deciding whether more or less charge is needed, therebyregulating the circuit current. −V_(in) 1614, capacitors 1618, andresistor 1620 and the ground terminal 1630 of the driver circuit 1604are all terminated to ground.

FIG. 17 is a schematic representation of an AC circuit used for atypical embodiment of a universal LED illumination device. Although thecircuits of FIG. 9 and FIG. 16 are well suited for DC operation of lowpower LEDs, FIG. 17 illustrates a typical AC circuit suitable fordriving a universal LED illumination device. In the case of bulbsintended for AC applications, a method can be used to rectify the ACvoltage to produce a DC signal as referred to above. However, circuitsthat merely rectify the AC voltage are best suited for use withbatteries and when the DC voltage available is less than or equal to theoperating voltage of the array of one or more LEDs. For example, withhalogen bulbs, a 14V AC source is often used as the power source and isexcessive for one or two LEDs. In this instance, an AC voltage regulatormay be used in conjunction with the LED that utilizes the inherentproperty of rectification of an LED that will generally withstand 5 V inreverse bias.

An alternating current voltage source is introduced to two IC regulatorcircuits 1704 and 1706 (i.e., National LM317) at V_(in) 1724 and V_(in)1734. The solid-state regulator circuits 1704 and 1706 regulate thepositive and negative going potential using the internal voltagereference of the IC and chop the sinusoidal input from, for example 14Vpeak-to-peak (P-P) to 3.6 V P-P to set the voltage output at V_(out)1728 and V_(out) 1738. Chopped outputs V_(out) 1728 and V_(out) 1738feed through parallel ladder path, the first rung containing resistor1720 and resistor 1730 in series, the second rung containing resistor1740 and resistor 1750 in series, and the third rung containing an LED1702. The first rung is connected between resistor 1720 and resistor1730 to a comparator input ADJ 1732 on regulator circuit 1704 and thesecond rung is connected between resistor 1740 and resistor 1750 to acomparator input ADJ 1742 on regulator circuit 1706. These comparatorinputs ADJ 1732 and ADJ 1742 are used as a feedback loop to compare theexternal voltage reference to an internal voltage reference V_(ref) toset the voltage output V_(out) 1728A and V_(out) 1738.

In this configuration, the ratio of resistor 1740/resistor 1750 (R3/R4)and resistor 1720/resistor 1730 (R1/R2) determine the positive andnegative voltage maximum. Here, the 14 V AC peak-to-peak signal isreduced to nearly a square wave with a 3.6V P-P max being used drive theLED 1702, using the LED 1702 to rectify the signal.

V_(out)+=V_(ref) (1.25 V) [1+(R1/R2)] is the positive going voltagemaximum and V_(out)−=V_(ref) (1.25V) [1+(R3/R4)] is the negative goingvoltage maximum.

Generally, the V_(out)—would be kept within a range well tolerated bythe reverse characteristics of the LED 1702.

What is claimed is:
 1. A method of retrofitting an illumination devicecomprising (i) a battery housing for containing at least one battery,(ii) an incandescent light source configured to be powered by the atleast one battery, and (iii) a reflector housing containing a reflectorfor reflecting light emitted by the incandescent light source toward anemission axis of the illumination device, the battery housing and thereflector housing collectively defining a volume envelope of theillumination device, the method comprising: replacing the incandescentlight source with a sub-assembly comprising (i) at least one solid-statelight emitter and (ii) a driving circuit for converting power from theat least one battery into suitable current to the at least onesolid-state light emitter; and replacing, within the reflector housing,the reflector with a replacement reflector for directing light emittedby the at least one solid-state light emitter along the emission axis,the replacement reflector having a size different from that of thereflector, wherein the replacements of the incandescent light source andthe reflector alter the internal configuration, but not the volumeenvelope, of the illumination device.
 2. The method of claim 1, whereinthe sub-assembly comprises a printed circuit board on which the at leastone solid-state light emitter and the driving circuit are disposed. 3.The method of claim 1, wherein the replacement reflector defines anopening therethrough through which the at least one solid-state lightemitter extends.
 4. The method of claim 1, wherein a shape of thereplacement reflector defines a portion of a paraboloid or a portion ofa cone.
 5. The method of claim 1, wherein the sub-assembly comprises aheat sink in thermal communication with the at least one solid-statelight emitter for conducting heat therefrom.
 6. The method of claim 1,wherein replacing the incandescent light source with the sub-assemblycomprises orienting the at least one solid-state light emittersubstantially parallel to the emission axis of the illumination device.7. The method of claim 1, wherein replacing the incandescent lightsource with the sub-assembly comprises orienting the at least onesolid-state light emitter substantially perpendicular to the emissionaxis of the illumination device.
 8. The method of claim 7, wherein thesub-assembly comprises a printed circuit board and the at least onesolid-state light emitter comprises at least one solid state-lightemitter disposed on each of two opposing surfaces of the printed circuitboard.
 9. The method of claim 1, wherein the at least one solid-statelight emitter comprises at least one light-emitting diode.
 10. Themethod of claim 1, wherein the driving circuit comprises ahigh-frequency DC-to-DC converter.
 11. The method of claim 1, wherein,to accommodate the sub-assembly, a dimension of the replacementreflector in a direction parallel to the emission axis of theillumination device is smaller than a corresponding dimension of thereflector.
 12. A method of retrofitting an illumination devicecomprising (i) a battery housing for containing at least one battery,(ii) an incandescent light source configured to be powered by the atleast one battery, and (iii) a reflector housing containing a reflectorfor reflecting light emitted by the incandescent light source toward anemission axis of the illumination device, the battery housing and thereflector housing collectively defining a volume envelope of theillumination device, the method comprising: replacing the incandescentlight source with a sub-assembly comprising (i) at least one solid-statelight emitter and (ii) a driving circuit for converting power from theat least one battery into suitable current to the at least onesolid-state light emitter, thereby reducing a volume of the batteryhousing, without altering the volume envelope of the illuminationdevice.
 13. The method of claim 12, further comprising replacing, withinthe reflector housing and without altering the volume envelope of theillumination device, the reflector with a replacement reflector fordirecting light emitted by the at least one solid-state light emitteralong the emission axis, the replacement reflector having a sizedifferent from that of the reflector.
 14. The method of claim 13,wherein, to accommodate the sub-assembly, a dimension of the replacementreflector in a direction parallel to the emission axis of theillumination device is smaller than a corresponding dimension of thereflector.
 15. The method of claim 12, wherein the sub-assemblycomprises a heat sink in thermal communication with the at least onesolid-state light emitter for conducting heat therefrom.
 16. The methodof claim 12, wherein replacing the incandescent light source with thesub-assembly comprises orienting the at least one solid-state lightemitter substantially parallel to the emission axis of the illuminationdevice.
 17. The method of claim 12, wherein replacing the incandescentlight source with the sub-assembly comprises orienting the at least onesolid-state light emitter substantially perpendicular to the emissionaxis of the illumination device.
 18. The method of claim 17, wherein thesub-assembly comprises a printed circuit board and the at least onesolid-state light emitter comprises at least one solid state-lightemitter disposed on each of two opposing surfaces of the printed circuitboard.
 19. The method of claim 12, wherein the at least one solid-statelight emitter comprises at least one light-emitting diode.
 20. Themethod of claim 12, wherein the driving circuit comprises ahigh-frequency DC-to-DC converter.